diff --git a/assets/scripts/Field.js b/assets/scripts/Field.js
new file mode 100644
index 0000000..df80f1a
--- /dev/null
+++ b/assets/scripts/Field.js
@@ -0,0 +1,34 @@
+/**
+ * Defines any key-value pair in any type of DNS-record
+ * Used for input fields on DNS creator pages
+ */
+export class Field {
+	displayName = null;
+	description = null;
+
+	constructor(key) {
+		this.key = key;
+	}
+
+	// Virtual methods
+
+	getInputHtml() {
+		return null;
+	}
+
+	getInputValue() {
+		return null;
+	}
+
+	// Builder methods
+
+	label(label) {
+		this.displayName = label;
+		return this;
+	}
+
+	desc(description) {
+		this.description = description;
+		return this;
+	}
+}
diff --git a/assets/scripts/records/DmarcRecord.js b/assets/scripts/records/DmarcRecord.js
index 59ece76..326a629 100644
--- a/assets/scripts/records/DmarcRecord.js
+++ b/assets/scripts/records/DmarcRecord.js
@@ -88,18 +88,4 @@ export class DmarcRecord extends TagListRecord {
 	constructor(text) {
 		super(text);
 	}
-
-	tokenize() {
-		return this.text
-			.replace(/;\s*$/, "")
-			.split(/;\s*/);
-	}
-
-	fieldsToString() {
-		let tokens = this.constructor.fields
-			.filter(field => !field.defaultValue || field.getInputValue() !== field.defaultValue)
-			.filter(field => field.getInputValue())
-			.map(field => field.key + "=" + field.getInputValue());
-		return tokens.join("; ");
-	}
 }
diff --git a/assets/scripts/records/SpfRecord.js b/assets/scripts/records/SpfRecord.js
index 799880f..a152c31 100644
--- a/assets/scripts/records/SpfRecord.js
+++ b/assets/scripts/records/SpfRecord.js
@@ -1,53 +1,43 @@
-import { Mechanism } from "../spf/Mechanism.js";
 import { ValidationError } from "../ValidationError.js";
 import { Modifier } from "../spf/Modifier.js";
 import { ValueRequirement } from "../spf/ValueRequirement.js";
+import { DomainMechanism } from "../spf/DomainMechanism.js";
+import { IPv4Mechanism } from "../spf/IPv4Mechanism.js";
+import { IPv6Mechanism } from "../spf/IPv6Mechanism.js";
+import { Mechanism } from "../spf/Mechanism.js";
+import { VersionTerm } from "../spf/VersionTerm.js";
 
 export class SpfRecord {
 	static fields = [
-		new Modifier("v")
+		new VersionTerm("v", "spf1")
 			.required()
-			.validate((key, val) => {
-				if (val !== "spf1") throw new ValidationError(`Version must be "spf1"`);
-				return true;
-			})
 			.pos(0),
 
-		new Mechanism("include")
-			.validate(this.validateDomain)
+		new DomainMechanism("include")
 			.multiple()
 			.pos(1),
 
-		new Mechanism("a")
-			.value(ValueRequirement.OPTIONAL)
-			.validate(this.validateDomain)
+		new DomainMechanism("a")
 			.multiple()
 			.pos(1),
 
-		new Mechanism("mx")
-			.value(ValueRequirement.OPTIONAL)
-			.validate(this.validateDomain)
+		new DomainMechanism("mx")
 			.multiple()
 			.pos(2),
 
-		new Mechanism("ptr")
-			.value(ValueRequirement.OPTIONAL)
-			.validate(() => { throw new ValidationError(`"ptr" mechanism should not be used`) })
+		new DomainMechanism("ptr")
 			.multiple()
 			.pos(2),
 
-		new Mechanism("ipv4")
-			.validate(this.validateIPv4)
+		new IPv4Mechanism("ipv4")
 			.multiple()
 			.pos(2),
 
-		new Mechanism("ipv6")
-			.validate(this.validateIPv6)
+		new IPv6Mechanism("ipv6")
 			.multiple()
 			.pos(2),
 
-		new Mechanism("exists")
-			.validate(this.validateDomain)
+		new DomainMechanism("exists")
 			.multiple()
 			.pos(2),
 
@@ -56,11 +46,9 @@ export class SpfRecord {
 			.pos(3),
 
 		new Modifier("redirect")
-			.validate(this.validateDomain)
 			.pos(4),
 
 		new Modifier("exp")
-			.validate(this.validateDomain)
 			.pos(4),
 	];
 
@@ -128,40 +116,9 @@ export class SpfRecord {
 				throw new ValidationError(`Term "${term.key}" must not have a value`);
 			}
 
-			if (input.value) term.validationFunction(term.key, input.value);
+			if (input.value) term.validate(input.value);
 
 			lastPos = term.position;
 		}
 	}
-
-	static validateDomain(key, value) {
-		// https://www.rfc-editor.org/rfc/rfc7208#section-7.1
-		const valid = value
-			.split(".")
-			.every(segment => segment.match(/^([^%]|%_|%%|%-|%\{[slodiphcrtv]\d*r?[-.+,\/_=]*})+$/));
-
-		if (!valid) throw new ValidationError(`Value for "${key}" is not a valid domain name`);
-
-		return true;
-	}
-
-	static validateIPv4(key, value) {
-		const segments = value.split(".");
-
-		const valid = segments.every(segment => {
-			const number = parseInt(segment);
-
-			return !isNaN(number) && number >= 0 && number <= 255;
-		});
-
-		if (segments.length !== 4 || !valid) {
-			throw new ValidationError(`Value for ${key} is not a valid IPv4 address`);
-		}
-
-		return true;
-	}
-
-	static validateIPv6(key, value) {
-		return true; // TODO validate properly
-	}
 }
diff --git a/assets/scripts/records/TagListRecord.js b/assets/scripts/records/TagListRecord.js
index 1379ca8..4706cce 100644
--- a/assets/scripts/records/TagListRecord.js
+++ b/assets/scripts/records/TagListRecord.js
@@ -9,7 +9,9 @@ export class TagListRecord {
 	}
 
 	tokenize() {
-		throw new Error("Unimplemented");
+		return this.text
+			.replace(/;\s*$/, "")
+			.split(/;\s*/);
 	}
 
 	getKeyValues() {
@@ -59,4 +61,12 @@ export class TagListRecord {
 
 		return true;
 	}
+
+	fieldsToString() {
+		let tokens = this.constructor.fields
+			.filter(field => !field.defaultValue || field.getInputValue() !== field.defaultValue)
+			.filter(field => field.getInputValue())
+			.map(field => field.key + "=" + field.getInputValue());
+		return tokens.join("; ");
+	}
 }
diff --git a/assets/scripts/spf/DomainMechanism.js b/assets/scripts/spf/DomainMechanism.js
new file mode 100644
index 0000000..08f0b5f
--- /dev/null
+++ b/assets/scripts/spf/DomainMechanism.js
@@ -0,0 +1,21 @@
+import { ValidationError } from "../ValidationError.js";
+import { Mechanism } from "./Mechanism.js";
+
+export class DomainMechanism extends Mechanism {
+	separator = ":";
+
+	constructor(key) {
+		super(key);
+	}
+
+	validate(value) {
+		// https://www.rfc-editor.org/rfc/rfc7208#section-7.1
+		const valid = value
+			.split(".")
+			.every(segment => segment.match(/^([^%]|%_|%%|%-|%\{[slodiphcrtv]\d*r?[-.+,\/_=]*})+$/));
+
+		if (!valid) throw new ValidationError(`Value for "${this.key}" is not a valid domain name`);
+
+		return true;
+	}
+}
diff --git a/assets/scripts/spf/IPv4Mechanism.js b/assets/scripts/spf/IPv4Mechanism.js
new file mode 100644
index 0000000..e6c3880
--- /dev/null
+++ b/assets/scripts/spf/IPv4Mechanism.js
@@ -0,0 +1,26 @@
+import { ValidationError } from "../ValidationError.js";
+import { Mechanism } from "./Mechanism.js";
+
+export class IPv4Mechanism extends Mechanism {
+	separator = ":";
+
+	constructor(key) {
+		super(key);
+	}
+
+	validate(value) {
+		const segments = value.split(".");
+
+		const valid = segments.every(segment => {
+			const number = parseInt(segment);
+
+			return !isNaN(number) && number >= 0 && number <= 255;
+		});
+
+		if (segments.length !== 4 || !valid) {
+			throw new ValidationError(`Value for ${key} is not a valid IPv4 address`);
+		}
+
+		return true;
+	}
+}
diff --git a/assets/scripts/spf/IPv6Mechanism.js b/assets/scripts/spf/IPv6Mechanism.js
new file mode 100644
index 0000000..a6c370a
--- /dev/null
+++ b/assets/scripts/spf/IPv6Mechanism.js
@@ -0,0 +1,12 @@
+import { Mechanism } from "./Mechanism.js";
+
+export class IPv6Mechanism extends Mechanism {
+	constructor(key) {
+		super(key);
+	}
+
+	validate(value) {
+		// TODO validate
+		return true;
+	}
+}
diff --git a/assets/scripts/spf/Modifier.js b/assets/scripts/spf/Modifier.js
index a64ffe7..639e072 100644
--- a/assets/scripts/spf/Modifier.js
+++ b/assets/scripts/spf/Modifier.js
@@ -1,4 +1,5 @@
 import { Term } from "./Term.js";
+import { ValidationError } from "../ValidationError.js";
 
 export class Modifier extends Term {
 	separator = "=";
@@ -6,4 +7,9 @@ export class Modifier extends Term {
 	constructor(key) {
 		super(key);
 	}
+
+	validate() {
+		// TODO validate
+		return true;
+	}
 }
diff --git a/assets/scripts/spf/Term.js b/assets/scripts/spf/Term.js
index 5cc81ed..a4a1db0 100644
--- a/assets/scripts/spf/Term.js
+++ b/assets/scripts/spf/Term.js
@@ -1,15 +1,15 @@
 import { ValueRequirement } from "./ValueRequirement.js";
+import { Field } from "../Field.js";
 
-export class Term {
+export class Term extends Field {
 	separator = null;
 	isRequired = false;
 	position = null;
 	allowMultiple = false;
 	valueRequirement = ValueRequirement.REQUIRED;
-	validationFunction = null;
 
 	constructor(key) {
-		this.key = key;
+		super(key)
 	}
 
 	// Builder methods
@@ -33,9 +33,4 @@ export class Term {
 		this.valueRequirement = requirement;
 		return this;
 	}
-
-	validate(func) {
-		this.validationFunction = func;
-		return this;
-	}
 }
diff --git a/assets/scripts/spf/VersionTerm.js b/assets/scripts/spf/VersionTerm.js
new file mode 100644
index 0000000..039220a
--- /dev/null
+++ b/assets/scripts/spf/VersionTerm.js
@@ -0,0 +1,17 @@
+import { Term } from "./Term.js";
+import { ValidationError } from "../ValidationError.js";
+
+export class VersionTerm extends Term {
+	separator = "=";
+
+	constructor(key, version) {
+		super(key);
+		this.version = version;
+	}
+
+	validate(value) {
+		if (value !== this.version) throw new ValidationError(`Version must be "${this.version}"`);
+
+		return true;
+	}
+}
diff --git a/assets/scripts/tags/Tag.js b/assets/scripts/tags/Tag.js
index e17cb04..9214b94 100644
--- a/assets/scripts/tags/Tag.js
+++ b/assets/scripts/tags/Tag.js
@@ -1,13 +1,14 @@
-export class Tag {
+import { Field } from "../Field.js";
+
+/** A tag within a DMARC/DKIM record */
+export class Tag extends Field {
 	isRequired = false;
 	defaultValue = null;
-	displayName = null;
-	description = null;
 	categoryName = null;
 	position = null;
 
 	constructor(key) {
-		this.key = key;
+		super(key);
 		this.id = "tag-" + key;
 	}
 
@@ -17,14 +18,6 @@ export class Tag {
 		return true;
 	}
 
-	getInputHtml() {
-		return null;
-	}
-
-	getInputValue() {
-		return null;
-	}
-
 	// Builder methods
 
 	required() {
@@ -37,16 +30,6 @@ export class Tag {
 		return this;
 	}
 
-	label(label) {
-		this.displayName = label;
-		return this;
-	}
-
-	desc(description) {
-		this.description = description;
-		return this;
-	}
-
 	category(category) {
 		this.categoryName = category;
 		return this;